When a mobile device (e.g., cell phone, UE) with an active or ongoing communication connection (e.g., voice or data call) is moving away from the coverage area of a first cell and entering the coverage area of a second cell, the communication connection is transferred to the second cell (target cell) in order to avoid link termination when the device gets out of coverage of the first cell (source cell). This “transfer of a connection” is termed handover or handoff. There may also be other reasons for performing a handover, such as load balancing.
In cellular networks, particularly 3GPP LTE heterogeneous networks, handover is becoming increasingly important for device mobility, particularly with the increasing use smaller cells and coverage areas overlaid with smaller cells. Some new use cases that are currently under discussion in 3GPP's RAN working groups (WGs) are dealing with “small-cell enhancements”. The concept of small-cell enhancements involves deployment of additional low-power nodes under the macro-layer coverage for capacity extension and coverage improvement purposes. In small-cell enhancement situations, devices need to be handed over between these smaller and larger cells.
One issue with handover is handover failure. Handover failure may occur during certain conditions, such as when a device is undergoing radio-link failure. When handover failure occurs, service interruption may occur. This service interruption may be unsuitable for many applications.
Thus, there are general needs for techniques to reduce handover failure. There are general needs for techniques to reduce the service interruption time resulting during handover failure. There are also general needs for improved handover techniques that reduce handover failure with small-cell enhancements.